The present invention relates generally to mass spectrometry and more particularly to systems and methods for optimizing the performance of a mass spectrometer system having multiple stages, such as a tandem mass spectrometer.
Mass spectrometry is an analytical technique used to measure the mass-to-charge ratio (m/z) of ions. A mass spectrometer is a device used for mass spectrometry, and produces a mass spectrum of a sample to find its composition. This is normally achieved by ionizing the sample and separating ions of differing masses and recording their relative abundance by measuring intensities of ion flux. A typical mass spectrometer comprises three parts: an ion source, a mass analyzer, and a detector.
Tandem mass spectrometry involves two or more stages of mass selection or analysis, usually separated by a stage of fragmentation. A tandem mass spectrometer is capable of multiple rounds of mass spectrometry. For example, in a first stage, one mass analyzer can isolate the ions of one compound from many compounds entering a mass spectrometer. The isolated compound ions (“precursor ions”) can then be fragmented in a second stage that includes a fragmentation region such as a collision cell. Compound ions are typically confined to the collision cell and stabilized via a multipole, and fragmented via collision-induced dissociation (CID) with inert gas molecules. A second mass analyzer then analyzes/separates the fragment ions produced from the compound ions, and the fragment ions are detected using a detection system. The result is a mass spectrum of the fragment ions for the isolated compound ions, commonly referred to as a MS/MS spectrum.
Often, a user may require the first mass analyzer to isolate many compounds consecutively, each of which may have many fragments that are to be analyzed by the second mass analyzer. Each time a new precursor ion or fragment is measured, the mass spectrometer requires time to stabilize the voltages, electrical fields and/or magnetic fields. The time it takes to stabilize the various system components is called the settling time. Thus, the overall analysis may take a significant amount of time. Additionally, the many compounds may be introduced into the first mass analyzer concurrently and over a limited time frame, such as across a liquid chromatography peak. For higher accuracy, repeated measurements of each transition from a precursor ion to its fragments may need to be made in the time frame a compound ion enters the mass spectrometer. As a competing concern for accuracy, the time spent on a single measurement, called the dwell time, should be as long as possible.
The time spent on a measurement is hindered by the time spent for the mass spectrometer to settle into a new setting for a new measurement.
Accordingly, it is desirable to provide systems and methods to obtain measurements at a faster acquisition rate and/or to maintain or increase the time spent on a single measurement, e.g., the dwell time.